A photoluminescent nano-material, which is typically referred to as nanodots, refers to a material having a nano-meter particle size to represent a specific light emission phenomenon. Photoluminescent nano-materials have been used for sensing, imaging, or solar cells according to inherent characteristics thereof. In particular, the photoluminescent nano-material is greatly expected in cell imaging, and the use value of the photoluminescent nano-material will be more increased in the future.
Photoluminescent nano-materials formed of CdS or CdSe, which have recently extensively used, may cause many problems in the use for the biological purpose, especially medical purpose due to the inherent heavy metal toxicity thereof.
On the one hand, although silicon (Si)-semiconductor quantum dots represent safety characteristics against the toxicity in the use for the biological purpose, especially medical purpose, the Si-semiconductor quantum dots do not represent excellent light emission stability.
Gold (Au)-nanodots or silver (Ag)-nanoclusters may have an economical problem in relation to the preparation cost.
In other words, there is a demand for a photoluminescent nano-material economically advantageous with safety in the biological use and stability in long-term light emission.
In addition, although carbon nanodots (C-DOT) represents a Φ value (measurement value of a photoluminescence emission spectrum) lower than that of a photoluminescent nanodots, the C-DOTs have been spotlighted in terms of chemical, optical, and biological safety.
However, conventionally, in order to obtain the carbon nanodots, a solvent, such as poly ethylene glycol (PEG), or strong acid is required, or a laser ablation scheme under high-temperature and high-pressure inert gas is required.
Therefore, it is necessary to more economically or more simply prepare the photoluminescent carbon nanodots.
Meanwhile, as a related art of the method for preparing the photoluminescent carbon nanodots according to an exemplary embodiment of the present invention, there is a coated water soluble nanoparticle disclosed in Korean Unexamined Patent Publication No. 10-2007-0059066 (published on Jun. 11, 2007).